Open
Description
https://suor.github.io/blog/2023/03/26/ban-1-plus-n-in-django/
Their example:
import logging
import os
from django.db.models.query_utils import DeferredAttribute
logger = logging.getLogger(__name__)
attrs_seen = set()
def _DeferredAttribute_get(self, instance, cls=None):
from django.conf import settings # monkeys go early, settings might not be available yet
if instance is None:
return self
data = instance.__dict__
field_name = self.field.attname
# Normally this accessor won't be called if field_name is in __dict__,
# we need this part so that DeferredAttribute descendants with __set__ play nice.
if field_name in data:
return data[field_name]
# If it's not there already then prevent an SQL query or at least notify we are doing smth bad
attr = f"{instance.__class__.__name__}.{field_name}"
# Only trigger this check once per attr to not flood Sentry with identical messages
if attr not in attrs_seen:
attrs_seen.add(attr)
message = f"Lazy fetching of {attr} may cause 1+N issue"
# We stop in DEBUG mode and if inside tests but let production to proceed.
# Using LookupError instead of AttributeError here to prevent higher level "handling" this.
if settings.DEBUG or "PYTEST_CURRENT_TEST" in os.environ:
raise LookupError(message)
else:
logger.exception(message)
# Proceed normally
return _DA_get_original.original(self, instance, cls)
_DA_get_original, DeferredAttribute.__get__ = DeferredAttribute.__get__, _DeferredAttribute_getMetadata
Metadata
Assignees
Labels
No labels